Panda is, by far, the most significant change in the algorithm I have seen in the 9 years I have been optimizing for search! The impact is far reaching and while it doesn’t fundamentally changes the core of a solid SEO strategy (which was always about good content), the massive long-tail strategies that have been successful for so long can kill your site. All content initiatives must proceed with extreme caution!!!   New sites that get off to the wrong start can have their domain poisoned from and they will never know.  Businesses that have been on the web for years can be destroyed overnight.  Many sites that were spared destruction in Panda 1, got hit with Panda 2 and Panda 3.   It is also much different than anything Google has done.  It is a site-wide 'penalty' ( although they insist it is not a penalty) and basically an admission that Google can not accurately judge the quality of an individual piece of content.   Contact me to discuss.